6: Loudness Perception
- Page ID
- 134604
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- Discuss how amplitude and frequency affect loudness perception
- Explain relationships among
- (sound) pressure amplitude
- sound intensity
- sound intensity level (SIL)
- sound pressure level (SPL)
- decibel (dB)
- Apply rules of thumb to solve problems involving decibels (indoors and outside)
- List decibel levels for some common sounds
- Explain how sound intensity changes with distance from the source (indoors and outside)
- Relate sound intensity level to hearing loss
Loudness is a qualitative impression formed inside the brain- it cannot be measured directly. However, scientists have made substantial progress understanding how the our perception of loudness depends on the properties of the vibrations that reach our ears. In previous parts of this book, you’ve learned that loudness perception is based mainly on amplitude, but that’s only part of the story. This part of the book will dig further into physically measurable characteristics of loud and soft sounds and how they impact human perception of loudness.
- 6.1: Pressure amplitude
- This page discusses how human hearing perceives loudness through sound wave pressure, emphasizing pressure amplitude's role. It explains that larger amplitudes equate to louder sounds, notes the range of detectable sounds, and differentiates "sound pressure" from air pressure. The concept of sound pressure level (SPL) in decibels is introduced, highlighting the challenges of perceiving loudness differences within a broad dynamic range of sound amplitudes.
- 6.2: Sound Intensity
- This page covers sound intensity, defined as energy flow measured in Watts per square meter (W/m²). It highlights the wide range of sound intensities from quiet to loud, linking intensity to pressure amplitude and noting that intensity adds linearly from multiple sources. Additionally, it explains that sound intensity diminishes with distance, underscoring the conservation of energy in sound propagation.
- 6.3: Decibels and sound levels
- This page covers the measurement of sound levels using the decibel (dB) scale and explains sound intensity level (SIL) and sound pressure level (SPL) as interchangeable concepts. It emphasizes that sound levels are relative to a reference sound, typically the threshold of hearing, and discusses the just noticeable difference (JND) in sound perception. Additionally, it highlights the risk of hearing loss from loud sounds and offers guidelines for hearing protection.
- 6.4: Decibels (the math)
- This page explains how to calculate sound intensity levels (SIL) in decibels using simple rules: doubling intensity increases SIL by 3 dB, and multiplying by ten increases it by 10 dB. It notes that intensities from multiple sources combine, but sound levels do not add linearly, using vacuum cleaners as an example.
- 6.5: Frequency and loudness perception
- This page outlines loudness perception, highlighting that amplitude and frequency both impact how loud sounds are perceived, with the human ear most sensitive to pitches between 300 Hz and 3000 Hz, especially around 1000 Hz. It introduces equal loudness contours (Fletcher-Munson curves) that demonstrate frequency's effect on loudness and their application in hearing tests.
- 6.6: Intensity and Distance
- This page explores sound intensity and its decrease with distance from the source, following the inverse square law. It illustrates that sound intensity diminishes as it spreads out, akin to spray paint distribution. Doubling the distance results in a 6 dB decrease in sound level, while a tenfold increase equates to a 20 dB decrease.
Thumbnail: Antique gramophone with vinyl record and stylus. (Unsplash License; Derek Wojcik on Unsplash)